1. Field of the Invention
This invention relates to a slide fastener slider in which a slider lock mechanism equipped in the slider automatically become operative to prevent the slider from further movement along element rows when a pull tab is released from fingers, and more particularly to an automatic lock slider suitable for both an ordinary slide fastener and a concealed slide fastener.
2. Description of the Related Art
Some of conventional slide fasteners of the ordinary type in which coupling element rows are exposed on the tape surfaces are equipped with a slider locking mechanism for keeping the slider from sliding unless a pull tab is pulled. In the most popular type of the conventional slider locking mechanisms, a locking pin projecting perpendicularly from a pintle of the pull tab comes into engagement with the element rows to prevent further movement of the slider when the pull tab is released from a pulling force to fall flat on the upper wing of the slider body.
In another conventional slider locking mechanism, as disclosed in, for example, Japanese Utility Model Publication No. SHO 62-41608, when the pull tab is pulled, a locking pawl formed on one end of a leaf spring whose other end is secured to the slider body is raised to be disengaged from the element rows, and when no pulling force is exerted on the pull tab, the locking pawl comes into engagement with the element rows through an aperture of the slider body under the resilience of the leaf spring to automatically prevent further movement of the slider.
However, if the foregoing conventional slider locking mechanism is applied to the concealed slide fastener in which the element rows are not exposed on the tape surfaces, the locking pin tends to pierce into the confronting inner edges of the opposed tapes concealing the opposed element rows from the outer side, so that the reliable locking function cannot be achieved on many occasions. Consequently, in the concealed slide fastener, it is customary to employ the above-mentioned slider locking mechanism so as to act on the back surfaces of the tapes where the coupling element rows come out.
This prior art is exemplified by U.S. Pat. Nos. 2,178,948 and 2,178,949. The automatic lock mechanism of the slider disclosed in these U.S. Patents is suitable for a kind of concealed slide fastener in which cloth or rubber tapes cover the majority of whole leg portions of the opposed element rows, with head portions exposed in the front tape surfaces. In this prior art lock mechanism, a pair of locking pawls projecting substantially perpendicularly from a right and left edges of a leaf spring, which is fixed at one end to the back surface of the slider body, and having a width substantially equal to the width of the back surface of the slider body, is brought into and out of engagement with the leg portions of adjacent elements of the individual element rows of opposed fastener stringers in the slider body, in response to pivotal or sliding movement of a pull tab when pulled.
Japanese Utility Model Publication No. SHO 54-31048 discloses an automatic lock slider for concealed slide fasteners. In the automatic lock slider, a pivotal bar connected to a pull tab has at its lower portion a pair of longitudinally confronting shoulders, and a leaf spring having at one end a locking pawl is fixed at the other end to the back surface of the slider body. As the pivotal bar is urged from its back side by the leaf spring, the shoulders are brought into engagement with the lower end of a through hole extending vertically in an element guide post of the slider body. Further, the through hole has a predetermined size such that the pivotal bar can be pivotally moved in the through hole. While the slider is not pulled, the locking pawls are brought into engagement with the element rows in the slider body to keep the slider from moving along the element rows. When the slider is pulled, the pivotal bar is pivotally moved in the through hole longitudinally of the slider body to deform the leaf spring against its resilience by the shoulders, thus releasing the locking pawls from the element rows. A concealed slide fastener has a stringer structure that is most popular in recent years. In the stringer structure, the element-row-attaching edge of each tape is bent in a U shape, and the individual element row is attached to the corresponding tape along the bent edge by sewing or other means. When the tapes of the concealed slide fastener are attached to a product, the element rows are located on the back side of the product.
With the automatic lock slider, for ordinary slide fasteners, disclosed in Japanese Utility Model Publication No. SHO 62-4160B, since the pintle of the pull tab and the leaf spring mounted on the slider body is concealed completely from outside by a covering, part of the slider projecting from the front surfaces of the opposed fastener stringers is necessarily larvae and hence tends to contact other things around and would have an unsightly appearance. Consequently, even in the ordinary slide fastener equipped with the automatic lock mechanism, it is strongly required to minimize part of the slider exposed from the front surfaces of opposed fastener stringers.
According to the automatic lock mechanism, for concealed slide fasteners, disclosed in the above-mentioned U.S. Patents, since the leaf spring is resiliently deformed via an actuating member in combination of the action of the pull tab and an associated cam mechanism, not only adequate precision is required in machining and assembling, but also reliable engagement and disengagement of the locking pawls with the elements cannot be guaranteed because the leaf spring is hard to deform due to its large width, depending on the movement of the pull tab. On the other hand, according to the automatic lock mechanism disclosed in Japanese Utility Model Publication No. SHO 54-31048, although it is simple in structure and hence is not so high machining precision, there is no guarantee that the pivotal bar is pivotally moved reliably, thus often causing unsmooth coupling and uncoupling of the locking pawl with the elements.